Shining A Light On Galactic Outflows: Photo-Ionized Outflows

We study the ionization structure of galactic outflows in 37 nearby, star forming galaxies with the Cosmic Origins Spectrograph on the Hubble Space Telescope. We use the O I, Si II, Si III, and Si IV ultraviolet absorption lines to characterize the different ionization states of outflowing gas. We measure the equivalent widths, line widths, and outflow velocities of the four transitions, and find shallow scaling relations between them and galactic stellar mass and star formation rate. Regardless of the ionization potential, lines of similar strength have similar velocities and line widths, indicating that the four transitions can be modeled as a co-moving phase. The Si equivalent width ratios (e.g. Si IV/Si II) have low dispersion, and little variation with stellar mass; while ratios with O I and Si vary by a factor of 2 for a given stellar mass. Photo-ionization models reproduce these equivalent width ratios, while shock models under predict the relative amount of high ionization gas. The photo-ionization models constrain the ionization parameter (U) between -2.25 < log(U) < -1.5, and require that the outflow metallicities are greater than 0.5 Z$_\odot$. We derive ionization fractions for the transitions, and show that the range of ionization parameters and stellar metallicities leads to a factor of 1.15-10 variation in the ionization fractions. Historically, mass outflow rates are calculated by converting a column density measurement from a single metal ion into a total Hydrogen column density using an ionization fraction, thus mass outflow rates are sensitive to the assumed ionization structure of the outflow.Comment: 30 pages, 17 tables, 14 figures. Accepted for publication in MNRA

Letter from J. A. Wofford to Gen. W. S. Featherston. 23 January 1869

Letter sent from Washington; regarding case of Mississippi before the Reconstruction Committee, amendment on elections, constitution, Republican Party. Envelope.https://egrove.olemiss.edu/ciwar_corresp/1262/thumbnail.jp

Carbon Abundances in Starburst Galaxies of the Local Universe

The cosmological origin of carbon, the fourth most abundant element in the Universe, is not well known and matter of heavy debate. We investigate the behavior of C/O to O/H in order to constrain the production mechanism of carbon. We measured emission-line intensities in a spectral range from 1600 to 10000 \AA\ on Space Telescope Imaging Spectrograph (STIS) long-slit spectra of 18 starburst galaxies in the local Universe. We determined chemical abundances through traditional nebular analysis and we used a Markov Chain Monte Carlo (MCMC) method to determine where our carbon and oxygen abundances lie in the parameter space. We conclude that our C and O abundance measurements are sensible. We analyzed the behavior of our sample in the [C/O] vs. [O/H] diagram with respect to other objects such as DLAs, neutral ISM measurements, and disk and halo stars, finding that each type of object seems to be located in a specific region of the diagram. Our sample shows a steeper C/O vs. O/H slope with respect to other samples, suggesting that massive stars contribute more to the production of C than N at higher metallicities, only for objects where massive stars are numerous; otherwise intermediate-mass stars dominate the C and N production.Comment: Accepted for publication in Ap

Evaluating White Clover for Resistance to Cylindrocladium Root Rot

A rapid screening technique was developed for use in evaluating white clover (Trifolium repens L.) for resistance to Cylindrocladium root rot incited by Cylindrocladium crotalariae. Culture plates of the fungus were evaluated for number of infective propagules after four weeks of growth on potato dextrose agar, and no differences were detected among plates. Seedlings of ‘Osceola’ white clover were exposed in the greenhouse to four levels of inoculum over a six-week period, with resistance based on percent survival of uninoculated controls. It was shown that suspending 1 culture plate in 100ml of water and rating plants four weeks after inoculation was suitable for screening seedlings. A field test was conducted to verify greenhouse results. Results indicated that the greenhouse technique gave similar results, and would be sufficient to use in a breeding program to develop resistance to this disease

Molecular Dynamics in Hydrogen‐bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field for HCN‐‐‐HF

Observation of the 2ν1 overtone band in the hydrogen‐bonded complex HCN‐‐‐HF permits evaluation of the anharmonicity constant X 1 1=−116.9(1) cm− 1 and determination of the anharmonicity corrected fundamental frequency ω1. This information, and available data from previous rovibrational analyses in the common and perdeuterated isotopic species of HCN‐‐‐HF, offer an opportunity for calculation of an approximate stretching harmonic force field. With the assumptions f 1 2=f 2 4=0.0, the remaining force constants (in mdyn/Å) are evaluated as: f 1 1=8.600(20), f 2 2=6.228(9), f 3 3=19.115(40), f 4 4=0.2413(39), f 1 3=0.000(13), f 1 4=0.0343(2), f 2 3=−0.211(6), f 3 4=0.000(2). These compare to f 1 1=9.658(2) in the HF monomer and f 1 1=6.244(3) and f 3 3=18.707(16) in the HCN monomer. These results provide the information necessary to quantitatively assess the applicability of the Cummings and Wood approximation in this hydrogen‐bonded complex and also give an estimate of D e j , the equilibrium distortion constant in the harmonic limit. Comparisons of these experimentally determined parameters with the predictions of a b i n i t i o molecular orbital calculations at several levels of approximation are presented

The Spectroscopy and Molecular Dynamics of the High Frequency ν1 6 Intermolecular Vibrations in HCN‐‐‐HF and DCN‐‐‐DF

Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν0 6 [ν0=1132.4783(2) cm− 1] in HCN‐‐‐HF and its corresponding perdeuterated fundamental ν1 6 [ν0=409.1660(2) cm− 1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K 6 6=537(17) and K 6 6 6 6=4.98(12) cm− 1 which in turn are used to estimate the pertinent cubic band stretching interaction constants K 4 6 6=−149.3(50) cm− 1 and account for the unexpected behavior in the rotational constantB 1 6. Second order expansion of the vibrational term energies, give X 4 6=−21.61(2), X 6 7=−7.694(1), X 6 6=−14.84(90), g 6 6=−31.04(90) cm− 1, neglecting corrections for Fermi resonance. The common isotopic species equilibrium rotational constantB e is evaluated to be 3681.1(11) MHz

Erratum: Determination of Dissociation Energies and Thermal Functions of Hydrogen Bond Formation Using High Resolution FTIR Spectroscopy [J. Chem. Phys. 8 7, 5674 (1987)]

Erratu

Finding a Fit: Biological Science Doctoral Students’ Selection of a Principal Investigator and Research Laboratory

In the laboratory-based disciplines, selection of a principal investigator (PI) and research laboratory (lab) indelibly shapes doctoral students’ experiences and educational outcomes. Framed by the theoretical concept of person–environment fit from within a socialization model, we use an inductive, qualitative approach to explore how a sample of 42 early-stage doctoral students enrolled in biological sciences programs made decisions about fitting with a PI and within a lab. Results illuminated a complex array of factors that students considered in selecting a PI, including PI relationship, mentoring style, and professional stability. Further, with regard to students’ lab selection, peers and research projects played an important role. Students actively conceptualized trade-offs among various dimensions of fit. Our findings also revealed cases in which students did not secure a position in their first (or second) choice labs and had to consider their potential fit with suboptimal placements (in terms of their initial assessments). Thus, these students weighted different factors of fit against the reality of needing to secure financial support to continue in their doctoral programs. We conclude by presenting and framing implications for students, PIs, and doctoral programs, and recommend providing transparency and candor around the PI and lab selection processes